The present invention concerns air cleaning processes and apparatus and more particularly such processes and apparatus adapted to remove paint overspray from air exhausted from paint spray booths.
In the production of automobiles, the surfaces of the car bodies are painted by a paint spraying process, typically conducted within a paint spray booth. The paint spraying operation inevitably results in paint overspray, i.e., a suspension of atomized paint in the surrounding air. The air in the spray booth must be continuously exhausted to prevent an excessive buildup of paint overspray in the air.
The air exhausted from the paint spray booth must have the suspended paint residual solids removed prior to its exhaust to the atmosphere. The conventional practice has been to pass the exhausted air through water washing air cleaners into which the paint solids are absorbed, causing the formation of a water-paint solid sludge.
While effectively removing the paint residuals from the exhausted air, the water washing process creates tremendous volumes of a water-paint sludge and it is difficult to handle and to dispose of the sludge.
Another approach, described in U.S. Pat. No. 4,257,783 to Gutjahr et al, utilizes a solid medium for collecting the paint solids by causing the paint to be deposited on solid surfaces. After drying, the paint solids are subsequently removed from the surfaces for disposal. In one version, a filtering conveyor carries an exposed surface which collects paint solids from the exhausted air, and various methods are used for subsequent removal of the dried paint from the conveyor surface, such as applying paint solvents and the like.
In a second embodiment described in that patent, the conveyor surface is cleaned by heated sand jets to mechanically remove the paint residuals. The mixture of the paint residuals and sand is then burned to eliminate the paint residuals from the mixture.
In yet another version, a bed of granular media, such as alumina, is utilized to absorb the paint residuals, with either solvents or burning utilized to remove the paint residuals to allow reuse of the alumina in the process.
All of these methods involve relatively complex apparatus including combustion chambers, etc., or require use of quantities of chemicals such as solvents.
Therefore, it is an object of the present invention to provide a process and apparatus for cleaning the air exhausted from paint spray booths of overspray paint residuals which does not involve water washing nor produce a sludge as a byproduct.
It is another object of the present invention to provide a process and apparatus for cleaning air exhausted from paint spray booths which is relatively simple and does not necessarily involve the use of paint solvents, or the burning of paint solids in combustion chambers, or the like.
It is still another object of the present invention to provide a process and apparatus for cleaning the air exhausted from paint spray booths which is economical in operation and does not necessitate the use of large quantities of energy or material in its performance.